import asyncio
import hashlib
import os
import re
import secrets
from time import time

from multidict import CIMultiDict
from devtools import debug


HOST = 'sip.soho66.co.uk'
PORT = 8060
CONN = HOST, PORT
USERNAME = os.environ['SIP_USERNAME']
PASSWORD = os.environ['SIP_PASSWORD']
URI = f'sip:{HOST}:{PORT}'
AUTH_METHOD = 'REGISTER'
BRANCH = secrets.token_hex()[:16].upper()


def md5digest(*args):
    return hashlib.md5(':'.join(args).encode()).hexdigest()


def parse_digest(header):
    params = {}
    for arg in header[7:].split(','):
        k, v = arg.strip().split('=', 1)
        if '="' in arg:
            v = v[1:-1]
        params[k] = v
    return params


RESPONSE_DECODE = re.compile(r'SIP/2.0 (?P<status_code>[0-9]{3}) (?P<status_message>.+)')
REQUEST_DECODE = re.compile(r'(?P<method>[A-Za-z]+) (?P<to_uri>.+) SIP/2.0')
NUMBER = re.compile(r'sip:(\d+)@')


def parse_headers(raw_headers):
    headers = CIMultiDict()
    decoded_headers = raw_headers.decode().split('\r\n')
    for line in decoded_headers[1:]:
        k, v = line.split(': ', 1)
        if k in headers:
            o = headers.setdefault(k, [])
            if not isinstance(o, list):
                o = [o]
            o.append(v)
            headers[k] = o
        else:
            headers[k] = v

    for regex in (REQUEST_DECODE, RESPONSE_DECODE):
        m = regex.match(decoded_headers[0])
        if m:
            return m.groupdict(), headers
    debug(raw_headers, headers)
    raise RuntimeError('unable to decode response')


class EchoClientProtocol:
    def __init__(self):
        self.transport = None
        self.auth_attempt = 0
        self.local_ip = None
        self.cseq = 1
        self.call_id = secrets.token_hex()[:10]
        self.last_invitation = 0

    def connection_made(self, transport):
        self.transport = transport
        self.local_ip, _ = transport.get_extra_info('sockname')
        print(f'connection established')
        self.send(f"""\
{AUTH_METHOD} sip:{HOST}:{PORT} SIP/2.0
Via: SIP/2.0/UDP {self.local_ip}:5060;rport;branch={BRANCH}
From: <sip:{USERNAME}@{HOST}:{PORT}>;tag=1269824498
To: <sip:{USERNAME}@{HOST}:{PORT}>
Call-ID: {self.call_id}
CSeq: {self.cseq} {AUTH_METHOD}
Contact: <sip:{USERNAME}@{self.local_ip};line=9ad550fb9d87b0f>
Max-Forwards: 70
User-Agent: TutorCruncher Address Book
Expires: 60
Content-Length: 0""")

    def datagram_received(self, data, addr):
        # print('datagram:', data)
        try:
            self.process_response(data, addr)
        except Exception:
            debug(data)
            debug(data.decode())
            raise

    def process_response(self, raw_data, addr):
        if raw_data == b'\x00\x00\x00\x00':
            return
        headers, data = raw_data.split(b'\r\n\r\n', 1)
        status, headers = parse_headers(headers)
        status_code = int(status.get('status_code', 0))
        if status_code == 401 and self.auth_attempt < 3:
            self.auth_attempt += 1
            auth = headers['WWW-Authenticate']
            params = parse_digest(auth)
            realm, nonce = params['realm'], params['nonce']
            ha1 = md5digest(USERNAME, realm, PASSWORD)
            ha2 = md5digest(AUTH_METHOD, URI)
            self.send(f"""\
{AUTH_METHOD} sip:{HOST}:{PORT} SIP/2.0
Via: SIP/2.0/UDP {self.local_ip}:5060;rport;branch={BRANCH}
From: <sip:{USERNAME}@{HOST}:{PORT}>;tag=1269824498
To: <sip:{USERNAME}@{HOST}:{PORT}>
Call-ID: {self.call_id}
CSeq: {self.cseq} {AUTH_METHOD}
Contact: <sip:{USERNAME}@{self.local_ip};line=9ad550fb9d87b0f>
Authorization: Digest username="{USERNAME}", realm="{realm}", nonce="{nonce}", uri="{URI}", \
response="{md5digest(ha1, nonce, ha2)}", algorithm=MD5
Max-Forwards: 70
User-Agent: TutorCruncher Address Book
Expires: 60
Content-Length: 0""")
        elif status_code == 200:
            print('authenticated successfully')
        elif status.get('method') == 'OPTIONS':
            # don't care
            pass
        elif status.get('method') == 'INVITE':
            n = time()
            if (n - self.last_invitation) > 1:
                self.process_invite(headers)
            self.last_invitation = n
        else:
            debug(status, dict(headers))
            try:
                data_text = data.decode()
            except UnicodeDecodeError:
                print(data)
            else:
                print(data_text)

    def send(self, data):
        data = (data.strip('\n ') + '\n\n').replace('\n', '\r\n').encode()
        self.transport.sendto(data)
        self.cseq += 1

    def error_received(self, exc):
        print('Error received:', exc)

    def process_invite(self, headers):
        m = NUMBER.search(headers['From'])
        if m:
            number = m.groups()[0]
        else:
            number = 'unknown'
            debug('no number found', dict(headers))
        country = headers.get('X-Brand', None)
        print(f'incoming call from {number}{" ({})".format(country) if country else ""}')


loop = asyncio.get_event_loop()
connect = loop.create_datagram_endpoint(lambda: EchoClientProtocol(), remote_addr=CONN)
transport, protocol = loop.run_until_complete(connect)
try:
    loop.run_forever()
except KeyboardInterrupt:
    pass
finally:
    transport.close()
    loop.close()